BENNINGTON — Police are treating an early-morning apartment fire as an act of arson.

Shortly after 3 a.m. Sunday, members of the Bennington Fire Department responded to an apartment building at 113 Gage St. With aid from Bennington Rural Fire Department, firefighters contained the blaze to a single apartment and had it extinguished within 30 minutes.

There were no injuries.

It was a large effort to get the blaze extinguished, said Steven Crawford, chief of the Bennington Fire Department.

“We probably had 40 firefighters and eight trucks on the scene,” Crawford said.

The apartment building contains four units. When firefighters arrived, residents from two of the units had already fled the building, while a resident in a third apartment was not home at the time.

When firefighters entered the fourth unit, they encountered a fire in the entryway. After extinguishing that blaze, firefighters found two additional fires in each of the bedrooms.

The fire was contained to the apartment, police said, with damages estimated at $20,000.

The apartment where the fire began was rented out but was not occupied at the time of the fire, Crawford said. A dog that resided in the apartment managed to escape the fire, according to Crawford.

Due to the suspicious nature of the fire, Crawford requested assistance to investigate the origin and cause of the blaze. Investigators with the Vermont State Police and the Division of Fire Safety responded to the scene and determined the fires were set intentionally.

The other apartment units sustained smoke damage, said Crawford. Two families have been temporarily displaced because firefighters had to cut electrical power to the building. They have been given shelter by the American Red Cross.

The Bennington Fire Department was assisted at the scene by the Bennington Rescue Squad and Bennington Police. Members of the North Bennington Fire Department covered the Bennington Fire Station.

The incident remains under investigation and anyone with information is asked to call State Police Sgt. Steven Otis at 875-2112, the Bennington Police Department at 442-1030 or the anonymous Vermont Arson Tip Line at (800) 322-7766.